As the mechanical seal with the partial impeller which cools the seal face by efficiently sending the cooling fluid (mainly cooling water) around the sliding seal face which generates the heat, conventionally, for example, the mechanical seal shown in FIG. 12 is known (refer to U.S. Pat. No. 4,290,611 (Patent document 1), JP Patent No. 3782690 (Patent document 2)).
The mechanical seal shown in FIG. 12 comprises a rotational ring 941 having a seal face S1, and a stationary ring 942 having a seal face S2; and the partial impeller 920 is formed on the inside of the sleeve 910 fitting on the rotary shaft 902. Also, a casing 930 is formed with a cooling fluid inlet bore 931 penetrating nearby a seal part 940, and a cooling fluid outlet bore 932 penetrating into the outer side from the nearby area of the partial impeller 920. These cooling fluid inlet bore 931 and cooling fluid outlet bore 932 are connected by the pipes which connects with the cooler 950 at the outside. The cooling fluid which flows into the nearby area of the seal part 940 from the cooling fluid inlet bore 931 cools the seal part 940 and flows out from the cooling fluid outlet bore 932, then recooled by the cooler 950 thereby it are designed to circulate.
The main function of such partial impeller 920 is to cool the heat generated at seal part 940, and the ability demanded is to provide the cooling fluid in a necessary flow rate.
Note that, as the shape of the partial impeller 920, a groove having an approximate half circular shape in its cross section, a groove having a conical shape of the cross section of half circular shape, and a groove having a cross section of a rectangular shape or so may be mentioned (for example, JP Utility Design No. H04-17569 (Patent document 3)).
Also the groove tip portion 920a on the inside of the partial impeller 920 approximately matches the end portion 933a on the inside of the groove 933 connecting to the cooling fluid outlet bore 932 of the casing 930.